VIBRATION PRONE MULTI-PURPOSE BUILDINGS AND TOWERS EFFECTIVELY DAMPED BY TUNED LIQUID COLUMN-GAS DAMPERS

Tuned mechanical dampers, TMD, are common practical passive devices to increase the effective structural damping. The sealed, tuned liquid column gas damper, TLCGD, became the cost-effective absorber of similar efficiency. Multi-purpose buildings and towers exhibit moderate or pronounced asymmetry even for a regular geometrical plan. Consequently, the floors are both, obliquely displaced and rotated about the vertical axis during earthquake or wind induced vibrations. The coupled, modal displacement and small rotation combine kinematically to a rotation about the floor’s modal center of velocity. If such a center falls outside of the floor (moderate asymmetry), the ideal position of the mid-plane of the U- or V- shaped TLCGD requires its normal distance from this center maximum. Pronounced asymmetry renders several modal centers within the floor plan: the novel (sealed, torsional) TTLCGD with its in plane curved piping section encloses the center for best efficiency. The uppermost floor is suitable to host all those modally tuned absorbers. For higher modes, a floor at intermediate height might become suitable. Tuning, in a first step becomes easy by means of the elaborated geometric analogy to the equivalent TMD or (torsional) TTMD. Subsequently performed fine tuning of frequency and damping in state-space renders an even more robust control, especially if smaller absorber units in parallel action are applied. The optimal absorber frequency is adjusted by assigning the equilibrium gas pressure, the novel control parameter resulting from the sealed design. Optimal damping of the fluid flow may require an orifice plate built in the piping system. Numerical simulations illustrate the effectiveness of these liquid absorbers to mitigate the earthquake or wind induced vibrations of plan-asymmetric buildings.